The Optical Transport Network (OTN) defined by the International Telecommunication Standardization Sector (ITU-T) is emerging as the core technology for telecommunications transport networks. The OTN provides an optimum converged transport technology for transparently carrying important legacy and emerging client signals over WDM networks. The OTN architecture is specified in ITU-T Rec. G.872 standard and the frame format and payload mappings are specified in the G.709 standard for carrying SONET/SDH, Ethernet and Storage Area Network (SAN) signals. GMP has been adopted as the mechanism for enabling the transport of all new client signals over the OTN, including the important Ethernet, video, and storage area network (SAN) signals.
The Generic Mapping Procedure (GMP) is a method for mapping arbitrary Constant Bit-Rate (CBR) client signals into Optical Transport Network (OTN) signals as specified by the ITU-T G.709 standard. At regular intervals within the OTN signal frame structure, the GMP overhead within the OTN signal communicates a count value related to the number of client bytes that will be transmitted in the OTN signal payload area during the next interval. This interval could be one frame or one multi-frame of the OTN Optical Data Unit (ODU) signal. The GMP payload byte placement algorithm is specified such that the receiver can determine, from the count value or the count information, OTN payload area bytes that contain client data and OTN payload area bytes that contain dummy or stuff data.